4 MICROSCOPIC EXAMINATION OF THE BLOOD. 



(</) The number exceeds 5,000,000 per cubic millimetre in the male, and 

 4,500,000 in the female ; so that, in 10 lbs. of blood, there are 25 billions of 

 corpuscles. The number is in inverse ratio to the amount of plasma ; hence, the 

 number must vary with the state of contraction of the blood-vessels, the pressure, 

 diffusion currents, and other conditions. 



The number of red corpuscles is increased ; in venous blood (especially in the small cutane- 

 ous veins), after the use of solid food, after much sweating, and the excretion of much -water by 

 the bowel and kidneys ; during inanition, because the blood-plasma undergoes decomposition 

 sooner than the blood-corpuscles themselves ; in the blood of the newly-born child, especially 

 when the umbilical cord is long in being tied ( 40), from the 4th day onward the number is 

 diminished ; in persons of robust constitution, and in those who live in the country. The 

 number is diminished, during pregnancy, after copious draughts of water. In the earlier 

 )ieriod of frvtal life the number is only 4-1 million in 1 cubic millimetre. (For the pathological 

 conditions sec S 10.) 



Methods of Counting the Blood-Corpuscles. The pointed end of a glass pipette (fig. 3), the 

 mixer, is dipped into the blood, and by sucking the elastic tube/, blood is drawn into the tube 



B 



ttIt 



r~ 



Kg. 2. 

 Apparatus of Abbe and Zeiss for counting the 

 corpuscles. A. in section ; C, surface view 

 without cover-glass ; 13, microscopic appear- 

 ance with the blood-corpuscles. 



Fig. 3. 



The Mclangtur, pipette 



or mixer. 



until it reaches the mark \, on the stem of the pipette, or until the mark 1 is reached. The 

 carefully-cleaned point of the pipette is dipped into the artificial serum, and this is sucked into 

 the pipette until it reaches the mark, 101. The artificial serum consists of 1 vol. of solution of 

 gum arable (sp. gr. 1020) and 3 vols, of a solution of equal parts of sodic sulphate and sodic 

 chloride (sp. gr. 1020). The process of mixing the two fluids is aided by the presence of a little 

 glass ball (a) m the bulb of the pipette. If blood is sucked up to the mark *, the strength of 

 the mixture is 1 : 200 ; if to the mark 1, it is 1 : 100 ; a small drop of the mixture is allowed to 

 run into the counting chamber of Abbe and Zeiss (fig. 2). The first portions are not used, ill 

 order to obtain a uniform sample from the bulb of the pipette. This chamber consists of a glass 



